Motorola Axiom CMD11E1 Guía de usuario descargar pdf (Pagina 28)

28 CHAPTER 2. INTRODUCTION TO LOOPING

>MM D000

D000 23 29

>C C000

29 41

P-C04B Y-AAAA X-D002 A-20 B-AA C-D9 S-004A

Using Loops

Here is a version using loops. We ﬁrst copy A to B. Then in a loop check if B is

greater than or equal to 10. If so, we subtract 10 from B and add 6 to A. If not,

we are done.

;;;;;;;;;;;;;;;;;;;;;;;;; START OF HEX2BCD ;;;;;;;;;;;;;;;

;

; THIS PROGRAM TAKES THE VALUE IN LOCATION $D000 AND

; CONVERTS IT TO ITS BCD REPRESENTATION AND STORES THE

; RESULT IN LOCATION $D001

;

; THE NUMBER IN LOCATION $D000 SHOULD BE BETWEEN 0 AND 99 ($63)

; NUMBERS BIGGER THAN 99 ARE IGNORED AND LEFT UNCHANGED.

; THE PROGRAM USES LOOPS AND REPEATED SUBTRACTION

OUT1BYT EQU $FFBB

OUT1BSP EQU $FFBE

ORG $C000

LDAA $D000

TAB *COPY A TO B

CMPB #10 *IS B < 10

BLO DONE *IF SO WE ARE DONE

SUBB #10 *B <- B-10

ADDA #6 *A <- A+6

BRA LT

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Motorola Axiom CMD11E1 Guía de usuario Pagina 28